As shown in FIG. 1, a heavy haul articulating dump truck is generally designated by the numeral 100. The articulating dump truck 100 is a vehicle that is constructed or assembled from two or more sections such as a cab 101 and a dump trailer 102. The cab 101 and the dump trailer 102 are pivotally joined together by an articulated joint 10. The dump trailer 102 is pivotal in the direction of the arrow D to dump a load therein and then return to a horizontal seated position. The articulated joint configuration provides greater capacity and flexibility of movement of the articulating vehicle dump truck thereby facilitating the control, steering and turning. While the articulated joint is shown in a articulated dump truck, such articulating joints are employed in other articulating vehicles including scrapers, tractor-trailers, heavy construction vehicles, buses, trams and trains. Typically, the articulated joint pivotally joins a structural frame member of each of the adjoining sections of the articulating vehicle by employing a bearing, for example a spherical plain bearing, received within the structural frame members. The articulated joint 10 may provide a permanent, semi-permanent or temporary pivotal connection between the structural frame members of the adjoining sections of the articulating vehicle.
As shown in FIGS. 9 and 10, a large mining wheel loader is generally designated by the numeral 200. The large mining wheel loader 200 generally includes a large mining device such as bucket 202 that is pivotally joined to tilt extension 212A by wishbone link 210A and to tilt extension 212B by wishbone link 210B. While the wishbone link 210A, 210B is shown in a large mining wheel loader 200, such wishbone links 210A, 210B are employed in other heavy duty vehicles. Typically, the wishbone link 210A, 210B employs a bearing, for example a spherical plain bearing, received within the structural frame members. The wishbone links 210A, 210B may provide a permanent, semi-permanent, or temporary pivotal connection between the bucket 202 and booms 204A, 204B of the loader 200.
The wishbone links 210A, 210B allow the bucket 202 to pivot in order to dump and scoop loose material. Traditionally, this cycle of dumping and scooping consists of three main phases. First, the operator places the bucket 202 on the ground, with its leading edge flush with or at a desired distance from the ground. The wheels 205 of the loader 200 advance the bucket 202, in addition to the loader 200, until the bucket 202 penetrates the material. In some cases this first phase is more difficult due to the properties of the material and/or lack of traction between the wheels 205 and ground. In this scenario, the operator may choose to repeatedly actuate the loader bucket tilt cylinders 208A, 208B as the loader 200 moves the bucket 202 further into the pile of material. Once a desired amount of material is contained in the bucket 202 the loader bucket lift cylinders 206A, 206B (not depicted) actuate to lift the bucket 202 to a desired height. The operator may then activate the wheels 205 to position the bucket 202 as needed. Lastly, the loader bucket tilt cylinders 208A, 208B activate to tilt the bucket 202 so that the material contained therein empties from the bucket 202. At this point the three phases can be repeated. Loaders 200 of the type disclosed herein are subjected to repeated series of these phases and the operator can engage the loader bucket lift cylinders 206A, 206B and the loader bucket tilt cylinders 208A, 208B in a number of different ways depending on the application. This movement places the bearings connecting the wishbone link 210A, 210B to the bucket 202 under considerable repeated stresses in an environment often filled with particulates that can contaminate the bearings.
Bearings, particularly spherical plain bearings, are necessary to reduce friction between moving parts of a mechanical assembly such as the structural frame members of the adjoining sections of the articulating vehicle or between the bucket and booms of a large mining wheel loader. Spherical bearing assemblies traditionally include an inner member positioned for rotational movement in relation to an outer member. The inner member typically includes a ball having a spherical outer diameter that defines an outer engagement surface and, typically, a bore passes through the ball. A shaft extends through the bore to pivotally secure the inner member to a portion of the structural frame or clevis. The outer member typically includes an outer ring having a spherical inner diameter that defines an inner engagement surface contoured to receive and retain the inner member therein. A lubricant gel, paste, or liquid such as grease, is typically provided between the inner member and the outer member; and between the inner member and the shaft, to reduce friction therebetween. Periodically the lubricant is replenished with a lubricant supply system. The replenishment of the lubricant helps flush debris out from between the inner member and the outer member. Spherical plain bearings used in the articulated joint of articulating vehicles and in the devises on buckets for large mining wheel loaders are subjected to small angle and high frequency oscillations. These conditions are not conducive for providing and replenishing lubrication to separate the sliding contacting surfaces of a spherical plain bearing and results in damage to such sliding contacting surfaces.
Seals extending between the inner member and the outer member and/or between the inner member and the shaft have been employed to retain the lubricant and to mitigate the influx of debris between the outer member and the inner member and between the inner member and the shaft. For example, a single SpreadLock® type seal is positioned in each single groove positioned on opposing sides of a spherical bearing, as described in U.S. Pat. No. 6,626,575, the subject matter of which is incorporated herein by reference. Typically, a single groove on each of opposing sides of the spherical bearing was employed to minimize the axial dimensions of the bearing while maximizing the load bearing capability of and sliding engagement between, the outer surface of the ball and the inner surface of the outer ring. However, space in the articulated joint can limit the type of seals that can be employed. For example, some articulated joints have two coaxially aligned bearings located in devises that have relatively tight clearances and limited space. Moreover, some seals do not keep all contaminants out of the bearing and can impair motion of the inner member relative to the outer member. In addition, movement of the inner member relative to the outer member can cause the seal to become dislodged. A means of preventing contaminant entry that would not impair relative motion of the inner member and the outer member, would better keep contaminants out of the bearing and would not allow the seal to be dislodged has long been sought in the industry.